Plant treatment agent is an agrochemically active substance or mixture thereof, whether naturally or synthetically derived, which is customary for the treatment of plants to modulate the growth, health and/or fertility thereof. Preferred plant treatment agents include, but are not limited to: pesticides (for example, acaricides, algicides, fungicides, bactericides, viricides, insecticides, aphicides, miticides, nematicides, molluscicides, and the like); gametocides; herbicides; defoliants; desiccants; plant-growth regulators (including growth hormones); fertilisers; plant nutrients; and mixtures thereof.
Preferably, the plant treatment agent maintains or enhances plant growth, health and/or fertility.
Although fertilisers in liquid form are convenient to apply, they are generally viewed as being environmentally disadvantageous due to product run-off into streams, rivers, aquifers and underground water catchments. Other forms of fertiliser may also lead to pollution problems such as eutrophication in bodies of water which are exposed to run-off from land that has been treated with the fertiliser, for example from land which has been aerially top dressed with superphosphate.
Several methods to control the release of nutrients to target plants and which significantly reduce pollution run-off have been disclosed.
In order to control ammonia volatilization and subsequently minimize the loss of ammonia, phosphoric acid and acidic phosphates have been used to control ammonia loss via reduction of microsite pH. However, apart from the high cost of amending these acidic materials, when they are mixed with urea, the end product is corrosive and such a product requires special precautions in handling and storage. Even if their use encourage formation of ammonium ions over ammonia gas, without good retention of the ammonium ions in the soil, efficient use of these ions by plants cannot be guaranteed as both ammonium and nitrate ions are subject to leaching. In addition, while plant nitrogen (N) can be decreased by the biological transformation of ammonium to nitrate, under anaerobic conditions, and nitrate can also be biologically denitrified to gases that lead to additional loss of N from soil.
In view of the above, it is advantageous to provide fertilisers that slowly release their nutrients to the target plants and which significantly reduce pollution run-off.